Liquid cooled electric motor frame

ABSTRACT

Liquid cooled electric motors including stator frames having cast in place cooling conduits are described. In an exemplary embodiment, the conduit is arranged in a generally helical configuration and the stator frame is cast around the conduit so that the conduit is embedded within, and integral with, the frame. Spacer, or stabilizer, bars are engaged to the conduit and provide support for the conduit and facilitate maintaining the desired spacing between lengths of conduit and between the conduit and the frame wall. The stator frame with the cast in place cooling conduit has the advantages of a liquid cooled motor yet is believed to be lower cost than known liquid cooled motors. The frame also is believed to be less susceptible to corrosion and liquid leaks as compared to known liquid cooled motors. Further, the advantage that the cooling coil and frame material may be different is provided, which enables selection of optimum material for the coil and frame with respect to cost, corrosion resistance, mechanical strength, and machinability.

FIELD OF THE INVENTION

This invention relates generally to electric motors and, moreparticularly, to a liquid cooled electric motor frame including a castin place cooling conduit and methods for fabricating such a motor frame.

BACKGROUND OF THE INVENTION

Electric motors generate heat during operation as a result of bothelectrical and mechanical losses, and an electric motor typically mustbe cooled in order to ensure the desired and efficient operation of themotor. An excessively high motor temperature may result in motor bearingfailure or damage to the stator winding insulation.

Electric motors generally have an enclosure, or housing, including aframe and endshields. The most common enclosures are "open" or totallyenclosed. With an "open" enclosure, ambient air circulates within theenclosure, and heat is removed by convection between the air and heatgenerating motor components within the enclosure. The air is exhaustedout from the enclosure.

Totally enclosed type enclosures typically are used in applications inwhich airborne contaminants, e.g., dirt, oil, or mist, must be preventedfrom entering within the enclosure. Both convection and conduction typecooling occurs within the enclosure, and some form of convection coolingoccurs at the external surfaces of the enclosure. For example, forcedconvection cooling is provided by a fan mounted to the motor shaftexternal the enclosure. The fan forces air over the frame andendshields. Alternatively, free convection and radiation type coolingmay occur if no shaft mounted fan is provided.

Known open and totally enclosed fan cooled motors generally require afan or compressor for circulating air over or through the motor.Providing the required air volume and velocity for proper cooling oftenresults in significant fan noise. Such noise can be reduced byeliminating the fan. Eliminating the fan, however, results in asignificant reduction in the cooling since the cooling coefficientsassociated with free convection and radiation type cooling aresignificantly lower than the cooling coefficients associated with forcedconvection cooling. Due to the lower cooling coefficients, a motorutilizing free convection and radiation type cooling must physically belarger than a forced air cooled motor, or the motor power output must bereduced as compared to the power output of the forced air cooled motor.

With the above described enclosures and cooling, heat from the motor isexchanged with ambient air in the immediate vicinity of the motor. Inmany applications, the heated ambient air must be continually refreshedwith cooler air in order to maintain proper motor cooling.

In a totally enclosed liquid cooled motor, the motor is connected to acoolant supply. The coolant supply is connected in a cooling circuit,which can be a closed loop or open loop type circuit. The liquid coolantcould, for example, be water, hydraulic oil, or other relatively lowtemperature process liquids.

In a closed loop system, the coolant is pumped through the motor andremoves the generated heat. The coolant is then circulated through aremotely mounted heat exchanger and returned to the motor. As oneexample, in a closed loop system the motor is connected to a coolingcircuit including a motor cooling coil, a circulating pump, an externalevaporative chiller, and associated piping.

In an open loop system, the coolant is not returned to the motor as inthe closed loop system. The coolant could, for example, be wasteliquids, process liquids, or any other available source of liquid thatfunctions as a coolant. As one example, in an open loop system, themotor is connected to a motor driven pump which pumps liquid from alarge reservoir, and a small percentage of the high-pressure fluidexiting the pump is diverted through the motor cooling coil and returnedto the reservoir.

The heat transfer coefficient for forced convection cooling using liquidis generally much higher, or better, than the heat transfer coefficientfor air. Therefore, in a liquid cooled motor, the overall coolingtypically is much better than a similarly sized, substantially similarair cooled motor. Further, in a liquid cooled motor, and by using aremotely mounted heat exchanger such as an evaporative water chiller,the immediate surroundings of the motor are not heated as with an aircooled motor. The remotely mounted heat exchanger therefore furtherfacilitates improving motor operation. Also, in a liquid cooled motor,the external fan can be eliminated which facilitates reducing motornoise.

In one known totally enclosed water cooled motor configuration, thestator frame includes a cooling jacket or passage, and a cooling mediumfrom an external source flows through the jacket and removes heatgenerated by the motor. Particularly, in known liquid cooled motors, thecooling jacket is formed by an inner shell and an outer shell. The innershell is machined to form a water path through the shell, and the outershell is then press fit or welded to the inner shell to form the waterjacket. Significant machining, welding, and assembly time are requiredto fabricate the above described water jacket. In addition, leakchecking and rework typically are required and further increase theframe cost.

The improved overall heat transfer of liquid cooling enables operationof the motor at a higher output for a particular motor size as comparedto an air cooled motor of the same size. Therefore, totally enclosedliquid cooled motors may be smaller than totally enclosed air cooledmotors having the same horse power ratings, even taking into account thewater jacket. The size of the motor affects, of course, the cost ofmotor components.

Also, known totally enclosed air cooled motors are believed to benoisier than liquid cooled motors since the liquid dampens at least someof the noise resulting from motor operation. The totally enclosed aircooled motor with an external fan generates significant noise due to airvelocity and turbulence. For example, an air cooled motor may operate atapproximately about 70-80 dBA, and a similarly rated liquid cooled motormay operate at approximately about 50 dBA.

Although liquid cooled motors are believed to provide many advantages,such motors also have disadvantages. For example, such motors typicallyare more expensive to fabricate than air cooled motors, and liquidcooled motors are susceptible to corrosion and to liquid leaks. Further,as corrosion builds-up within the cooling jacket over time, the overallheat transfer capability of the water cooled motor degrades.

It would be desirable to provide the many advantages of a liquid cooledmotor yet at a lower cost than known liquid cooled motors. It also wouldbe desirable to provide a liquid cooled motor that has a reducedsusceptibility to corrosion and liquid leaks as compared to known liquidcooled motors.

An object of the present invention is to provide a low cost liquidcooled motor.

Another object of the present invention is to provide such a liquidcooled motor which is less susceptible to corrosion and liquid leaksthan known liquid cooled motors.

Still another object of the invention is to provide a simplified andlower cost process for fabricating liquid cooled motors.

Yet another object of the present invention is to provide an integralcooling jacket and stator frame for reducing the labor required infabricating a liquid cooled motor as compared to the labor required inknown liquid cooled motors.

SUMMARY OF THE INVENTION

These and other objects may be attained with a liquid cooled electricmotor including a stator frame having a cast in place cooling conduit.In an exemplary embodiment, the conduit is arranged in a generallyhelical geometric configuration and the stator frame is cast around theconduit so that the conduit is embedded within, and integral with, theframe. Spacer, or stabilizer, bars are engaged to the conduit andprovide support for the conduit and facilitate maintaining the desiredspacing between lengths of the conduit. The spacer bars also facilitatecentering the coil in the cast frame wall and locate, or orient, thecooling coil axially within the frame during the casting process. Inaddition, the spacer bars facilitate determining the concentricity ofthe cooling coil with respect to the stator frame bore prior to thestator frame machining process, which reduces the possibility ofdamaging the cooling coil during such machining. The stator frame alsoincludes a cooling inlet port and a cooling outlet port in flowcommunication with the cast in place cooling conduit.

Of course, many alternative configurations for the cooling conduit arepossible and contemplated. For example, the cooling conduit describedabove provides that the cooling medium flows around, orcircumferentially, with respect to the motor stator. Alternatively, andby way of example, the cooling conduit could be configured so that thecooling medium flows substantially axially with respect to the motorstator. Various alternative configurations of cooling conduits aredescribed herein.

Prior to operation of a motor including the above described stator framehaving the cast in place cooling conduit, the frame inlet and outletports are coupled in a closed loop cooling circuit which includes, forexample, a pump and a remote heat exchanger. In operation, a coolingmedium such as water flows through the cooling circuit. Particularly, tocool the motor during operation, the cooling medium is delivered to theinlet port and flows through the conduit to the outlet port. As thecooling medium flows through the conduit, heat generated by the motor istransferred to the cooling medium through the conduit. The heatedcooling medium then flows out of the frame through the outlet port, andthe heated cooling medium is then pumped by the cooling circuit pump.The cooling medium is circulated through a remote heat exchanger so thatthe cooling medium is cooled and then delivered to the inlet port.

The cast in cooling coil can be fabricated from a metal different fromthe metal used in casting the frame. For example, the casting materialmay be gray iron and the coil may be stainless steel to take advantageof the mechanical dampening characteristics of the gray iron and thecorrosion resistance of the stainless steel. Alternatively, the castingmaterial may be aluminum alloy which is easy to machine and has a highthermal conductivity. In known enclosures for water cooled motors, inorder to provide the corrosion resistance of stainless steel, the entireframe generally must be cast from stainless steel, which is expensive.In the above described cast in coil construction, the coil can bestainless steel and the casting material can be a lower cost and easierto machine material.

The above described motor including the stator frame with the cast inplace cooling conduit has the advantages of a liquid cooled motor yet isbelieved to be lower cost than known liquid cooled motors. Such lowercost is achieved by providing that the preformed cooling conduit issimply cast in place rather than requiring the significant machining,welding, and assembly time associated with known water jackets. Themotor also is believed to be less susceptible to corrosion and liquidleaks as compared to known liquid cooled motors. Specifically, since thecorrosion resistant, continuous, and sealed cooling conduit is cast inplace in the stator frame, the possibility for leaks and internal coilor external frame corrosion are believed to be reduced as compared thepossibility for leaks and corrosion which may result with known waterjackets.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation view of a motor.

FIG. 2 is a front elevation view of the motor shown in FIG. 1.

FIG. 3 is partial cross-section view through the motor shown in FIG. 1.

FIG. 4 is a front view of the cooling conduit utilized in connectionwith the motor shown in FIG. 1.

FIG. 5 is a side elevation view of the conduit shown in FIG. 4.

FIG. 6 is a perspective view of the conduit shown in FIG. 4.

FIG. 7 is a perspective view of an alternative embodiment of a coolingconduit.

FIG. 8 is a perspective view of yet another alternative embodiment of acooling conduit.

FIG. 9 is a partial cross-section view through mold tooling utilized tocast the stator frame integrally with the cooling tube conduit shown inFIG. 6.

FIG. 10 is a partial cross-section view through mold tooling utilized tocast foam integrally with the cooling tube conduit shown in FIG. 6 inconnection with performing a lost foam fabrication method.

FIG. 11 is a perspective view of a cooling conduit embedded in foam asresult of the operation performed utilizing the tooling shown in FIG.10.

DETAILED DESCRIPTION

FIG. 1 is a side elevation view of a liquid cooled electric motor 100including a stator frame 102 having a cast in place cooling conduit (notshown in FIG. 1), as described hereinafter in more detail. The cast inplace cooling conduit defines a cooling passageway, or path, throughframe 102. By casting the cooling conduit in stator frame 102, it isbelieved that the many advantages of liquid cooling can be provided at alower cost than known liquid cooled motors. Further, the cast in placecooling conduit structure results in stator frame 102 and the coolingpassage having reduced susceptibility to corrosion and liquid leaks ascompared to stator frames and cooling passages of known liquid cooledmotors.

More particularly, and referring to FIGS. 1 and 2, stator frame 102includes a substantially cylindrical shaped body section 104 havingopposed ends 106 and 108. A cooling inlet port 110 and a cooling outletport 112 are in flow communication with the cast in place coolingconduit (not shown in FIGS. 1 and 2). Frame 102 also includes supportfeet 114 and lifting lugs or eye bolts 116. Bolt openings 118 areprovided in support feet 114 so that motor 100 can be bolted, ifdesired, in place. End shields 120 and 122 are secured to frame 102 bybolts 124 and close ends 106 and 108 of frame 102. Assembled end shields120 and 122 and frame 102 sometimes are referred to as the enclosure ormotor housing.

A stator core and windings (not shown) are secured within the motorhousing, as is well known. A rotor shaft 124 is rotatably mounted withinthe housing and rotates relative to frame 102. A conduit box 126 issecured to stator frame 102, and conduit box 126 includes lead cablestrain reliefs 128 positioned adjacent openings in conduit box 126.Power and control leads (not shown) extend through the openings inconduit box 126 and are electrically connected, for example, to thestator windings.

FIG. 3 is a partial cross-section view through motor 100. As shown inFIG. 3, bearing assemblies 130 and 132 are supported by end shields 120and 122, and bearing assemblies 130 and 132 include bearings 134 and 136for supporting rotor shaft 124. Grease inlet tubes 138 and 140 in flowcommunication with bearing assemblies 130 and 132 extend through endshields 120 and 122 and enable an operator to supply grease to bearings134 and 136.

Still referring to FIG. 3, cooling conduit 142 is located in statorframe 102. Frame 102 includes a substantially cylindrical shaped bodysection 144 formed by a wall 146 having an outer surface 148 and aninner surface 150. The cooling passageway is at least partially withinwall 146 between inner and outer surfaces 148 and 150. Particularly,conduit 142 (sometimes referred to as a tube coil) has a generallyhelical geometric shape and extends along a length of frame 102. Spacer,or stabilizer, bars 152 are engaged to conduit 142.

Referring to FIGS. 4, 5 and 6, which are front, side, and perspectiveviews, respectively, of cooling conduit 142, conduit 142 includes aninlet end 154 and an outlet end 156. Enlarged tube sections 158 and 160are located at ends 154 and 156 and align with inlet and outlet ports110 and 112 in frame 102 (FIG. 1). An intermediate portion 162 ofconduit 142 has a generally helical geometric shape. Spacer bars 152engaged to conduit 142 provide support for conduit 142 and maintain thedesired spacing between lengths, or turns, of conduit 142. Spacer bars152 also facilitate centering conduit 142 within the cast frame wall andlocating conduit 142 axially within the frame wall during the castingprocess. Spacer bars 152 also can be used determine the concentricity ofcooling conduit 142 with respect to the stator frame bore prior to themachining process, which reduces the possibility of damaging conduit 142during stator frame machining operations.

With respect to motor 100 (FIG. 1), and prior to operation, inlet andoutlet ports 110 and 112 are coupled in a closed loop cooling circuitwhich includes, for example, a pump and a remote heat exchanger.Alternatively, an open loop cooling circuit could be used. In operation,a cooling medium such as water flows through the cooling circuit.Particularly, to cool motor 100 during operation, the cooling medium isdelivered to inlet port 110 and flows through conduit 142 to outlet port112. As the cooling medium flows through conduit 142, heat generated bymotor 100 is transferred to the medium through conduit 142. The heatedcooling medium then flows out of frame 102 through outlet port 112, andthe heated cooling medium is then pumped by the cooling circuit. Thepumped cooling medium is circulated through a remote heat exchanger andreturned to inlet port 110.

Motor 100 including stator frame 102 with cast in place cooling conduit142 has the advantages of a liquid cooled motor yet is believed to belower cost than known liquid cooled motors. Such lower cost is achievedby providing that preformed cooling conduit 142 is simply cast in placerather than requiring the significant machining, welding, and assemblytime associated with known water jackets. Also, the material used incasting frame 102 can be selected to further reduce machining costs.

In addition, motor 100 is believed to be less susceptible to corrosionand liquid leaks as compared to known liquid cooled motors.Specifically, since cooling conduit 142 is cast in place in frame 102,the possibility for leaks and internal corrosion are believed to bereduced as compared the possibility for leaks and corrosion which mayresult with known water jackets. The cooling conduit material may alsobe selected to provide optimum corrosion resistance independent of theframe wall material. For example, the cooling conduit material may bestainless steel and the frame material may be gray iron.

Cooling conduit 142 provides that the cooling medium flows around, orcircumferentially, with respect the motor stator. Of course, the cast inplace cooling conduit is not limited to the exemplary helicalconfiguration shown in the drawings discussed above. The cooling conduitcan have many alternative geometric configurations.

For example, FIG. 7 is a perspective view of an alternative embodimentof a cooling conduit 200 having a squirrel cage configuration. Althoughshown by itself in FIG. 7, it should be understood that conduit 200would be cast in place in a motor frame. Opposing ends 202 and 204 ofconduit 200 include tube rings 206 and 208 having a generally circularshape, and straight tube segments 210 are coupled to and extend betweenrings 206 and 208. Each tube segment 210 is in flow communication witheach ring 206 and 208. Tube rings 206 and 208 and tube segments 210 formthe squirrel cage configuration of conduit 200. Inlet and outlet tubes212 and 214 are coupled to one of respective rings 206 and 208. Enlargedtube sections 216 and 218 are located at the ends of tubes 212 and 214and align with, for example, inlet and outlet ports 110 and 112 of frame102 (FIG. 1). Spacer bars 220 are engaged at opposing ends 202 and 204to respective rings 206 and 208 to provide support and extra rigidityfor conduit 200. Spacer bars 220 also facilitate centering conduit 200within the cast frame wall and locating conduit 200 axially within theframe wall during the casting process. Spacer bars 220 also can be useddetermine the concentricity of cooling conduit 200 with respect to thestator frame bore prior to the machining process, which reduces thepossibility of damaging conduit 200 during stator frame machiningoperations.

With squirrel cage conduit 200, and prior to operation, inlet and outlettubes 212 and 214 are coupled in a cooling circuit which includes, forexample, a pump. In operation, a cooling medium such as water flowsthrough the cooling circuit. The heated cooling medium from the motor ispumped through a remote heat exchanger, and is returned to inlet tube212.

FIG. 8 is a perspective view of yet another alternative embodiment of acooling conduit 250. Although shown by itself in FIG. 8, it should beunderstood that conduit 250 would be cast in place in a motor frame.Rather than a circumferential flow pattern as provided with coolingconduit 142 (FIG. 6), water flows through conduit 250 in an axial flowpattern. Particularly, conduit 250 includes an inlet end 252 and anoutlet end 254. Enlarged tube sections 256 and 258 are located at ends252 and 254 and align with inlet and outlet ports 110 and 112 of frame102 (FIG. 1). An intermediate portion 260 of conduit 250 has a generallyserpentine geometric shape. Spacer bars (not shown) may be engaged toconduit 250 to provide support for conduit 250 and maintain the desiredspacing between lengths, or turns, of conduit 250. The spacer bars alsofacilitate centering conduit 250 within the cast frame wall and locatingconduit 250 axially within the frame wall during the casting process.The spacer bars also can be used determine the concentricity of coolingconduit 250 with respect to the stator frame bore prior to the machiningprocess, which reduces the possibility of damaging conduit 250 duringstator frame machining operations.

Prior to operation, inlet and outlet ends 252 and 254 are coupled in acooling circuit which includes, for example, a pump and remote heatexchanger. In operation, the cooling medium is delivered to inlet end252 and flows through conduit 250 to outlet end 254. As the coolingmedium flows through conduit 250, heat is transferred to the mediumthrough conduit 250. The heated cooling medium is then pumped by thecooling circuit pump through the remote heat exchanger, and the coolingmedium is returned to inlet end 252.

While exemplary embodiments of the cooling conduit have been describedabove, it is contemplated that the cooling conduit can have many otherconfigurations. Therefore, it should be understood that the presentinvention is not limited to any particular geometric configuration ofthe cooling conduit.

Further, it is contemplated that cooling conduit can be totallyeliminated by casting the stator frame to include a cooling passagewaydefined by the walls of the stator frame. Such a cooling passageway canbe formed, for example, by including mold tooling defining an internalpassageway through the stator frame.

With respect to fabrication of stator frame 102 (FIG. 1), FIG. 9 is apartial cross-section view through mold tooling 300 utilized in castingstator frame 102 around, and integrally with, cooling tube conduit 142.Prior to the casting operation, cooling conduit 142 is formed into thehelical configuration from materials suitable for use as a cooling coiland suitable for use with the casting process, such as stainless steel.

Conduit 142 may be filled with sand to prevent collapsing during thecasting process. Conduit 142 typically is cleaned and pre-treated with aflux material to ensure adhesion of the cast metal to conduit 142 duringthe metal solidification process.

As is well known, mold tooling 300 can be fabricated using sand castingtechniques. Preformed conduit 142 is positioned within a mold toolingcavity 302, and positioners 304 are utilized to position conduit 142within cavity 302. Positioners 304 are integral with mold tooling 300.Alternatively, positioners 304 can be fabricated from metal, ceramic, orfoam and adhesively secured to mold tooling 300.

Once conduit 142 is positioned within mold tooling 300 as shown in FIG.9, frame 102 is cast around conduit 142 using a metal casting process.Alternatively, frame 102 can be cast from gray iron, ductile iron,steel, or a metal alloy. Metal casting processes are well known.

Once the molten metal cools, the frame and conduit assembly is removedfrom mold tooling 300, and cleaned and inspected to ensure integrity hasbeen maintained. In addition, if sand has been placed within conduit142, the sand is blown out of conduit.

The stator frame fabrication process described above is believed to bemuch more simple and lower cost in terms of both material and labor thanknown processes for fabrication of known water jackets. In addition, andas explained above, since conduit 142 is molded or cast integral withframe 102, the above described stator frame and conduit assembly isbelieved to be less susceptible to leakage and corrosion than the knownconstructions. Also, the materials for the stator frame walls and forthe conduit may be selected separately, or substantially independently,to achieve best cost and performance for the particular motor.

Of course, other processes can be used to fabricate the stator frame andcooling conduit assembly. For example, a lost foam casting process canbe used. Particularly, FIG. 10 is a partial cross-section view throughmold tooling 350 utilized to cast foam around cooling conduit 142.Cooling conduit 142 is formed into the helical configuration prior tothe casting operation. Conduit 142 may be filled with sand to preventcollapsing during the casting process. Conduit 142 is cleaned andpre-treated with a flux material to ensure adhesion of the cast metal toconduit 142 during the metal solidification process.

Mold tooling 350 includes an upper mold tool 352 and a lower mold tool354. Mold tooling 350 can be fabricated using well known techniques, andincludes integral positioning fingers 356.

Once conduit 142 is positioned within mold tooling 350 as shown in FIG.10, foam is then injected into mold tooling 350 and solidifies aroundconduit 142 to form a rigid foam structure 358 (FIG. 11). Rigid foamstructure 358 is then removed from mold tooling 350. An exemplaryembodiment of such rigid foam structure 358 is illustrated in FIG. 11.

After structure 358 is removed from mold tooling 350, foam structure 358is then positioned within metal casting tooling, and frame 102 is castaround conduit 142. As is well known, foam vaporizes during the metalcasting process.

The mold tooling required for the lost foam casting process is believedto be more expensive than the tooling required in the process describedin connection with FIG. 9. However, the lost foam casting process isbelieved to be much more simple and lower cost in terms of both materialand labor than known processes for fabrication of steel frames and waterjackets. In addition, the lost foam process may result in frames of moreconsistent quality, or repeatability, than other casting processes.

From the preceding description of several embodiments of the presentinvention, it is evident that the objects of the invention are attained.Although the invention has been described and illustrated in detail, itis to be clearly understood that the same is intended by way ofillustration and example only and is not to be taken by way oflimitation. Accordingly, the spirit and scope of the inventions are tobe limited only by the terms of the appended claims.

What is claimed is:
 1. A stator frame for an electric motor, said statorframe comprising:a substantially cylindrical shaped body section havingopposed ends, and a cooling passageway extending through at least aportion of said body section, said cooling passageway comprises acooling conduit; an inlet port and an outlet port in flow communicationwith said cooling passageway; and at least one spacer bar engaged tosaid cooling conduit.
 2. A stator frame in accordance with claim 1wherein said body section comprises a wall having an outer surface andan inner surface, and said cooling passageway is at least partiallywithin said wall between said inner surface and said outer surface.
 3. Astator frame in accordance with claim 1 wherein said cooling conduitcomprises an inlet end positioned at said inlet port and an outlet endpositioned at said outlet port.
 4. A stator frame in accordance withclaim 3 wherein said cooling conduit further comprises an intermediateportion between said inlet end and said outlet end.
 5. A stator frame inaccordance with claim 4 wherein said cooling conduit intermediateportion is arranged in a generally helical geometric configuration.
 6. Astator frame in accordance with claim 4 wherein said cooling conduitintermediate portion is arranged in a generally serpentine geometricconfiguration.
 7. A stator frame for an electric motor, said statorframe comprising:a substantially cylindrical shaped body section havingopposed ends, and a cooling passageway extending through at least aportion of said body section, said cooling passageway comprises acooling conduit comprising an inlet end and an outlet end, said coolingconduit further comprising first and second tube rings having agenerally circular shape, and a plurality of straight tube segmentscoupled to and extending between said first and second rings; and aninlet port and an outlet port in flow communication with said coolingpassageway, said inlet end positioned at said inlet port and said outletend positioned at said outlet port.
 8. A stator frame in accordance withclaim 7 wherein an inlet tube is coupled to said first ring and anoutlet tube is coupled to said second ring.
 9. A stator frame inaccordance with claim 3 wherein said cooling conduit is a first materialand said body section is a second material.
 10. An electric motor,comprising:a stator frame comprising a substantially cylindrical shapedbody section having opposed first and second ends, and a coolingpassageway extending through at least a portion of said body section,said frame further comprising an inlet port and an outlet port in flowcommunication with said cooling passageway, said cooling passagewaycomprises a cooling conduit; a first end shield secured to said firststator frame end; a second end shield secured to said second statorframe end; and at least one spacer bar engaged to said cooling conduit.11. An electric motor in accordance with claim 10 wherein said statorframe further comprises a plurality of support feet and lifting lugsextending from said body section.
 12. An electric motor in accordancewith claim 10 wherein said stator frame body section comprises a wallhaving an outer surface and an inner surface, and said coolingpassageway is at least partially within said wall between said innersurface and said outer surface.
 13. An electric motor in accordance withclaim 10 wherein said cooling conduit comprises an inlet end positionedat said inlet port and an outlet end positioned at said outlet port. 14.An electric motor in accordance with claim 13 wherein said coolingconduit further comprises an intermediate portion between said inlet endand said outlet end.
 15. A stator frame in accordance with claim 14wherein said cooling conduit intermediate portion is arranged in agenerally helical geometric configuration.
 16. A stator frame inaccordance with claim 14 wherein said cooling conduit intermediateportion is arranged in a generally serpentine geometric configuration.17. An electric motor, comprising:a stator frame comprising asubstantially cylindrical shaped body section having opposed first andsecond ends, and a cooling passageway extending through at least aportion of said body section, said frame further comprising an inletport and an outlet port in flow communication with said coolingpassageway, said cooling passageway comprises a cooling conduitcomprising first and second tube rings having a generally circularshape, and a plurality of straight tube segments coupled to andextending between said first and second rings; a first end shieldsecured to said first stator frame end; and a second end shield securedto said second stator frame end.
 18. A stator frame in accordance withclaim 17 wherein an inlet tube is coupled to said first ring and anoutlet tube is coupled to said second ring.
 19. A stator frame inaccordance with claim 13 wherein said cooling conduit is a firstmaterial and said body section is a second material.
 20. A method forfabricating a stator frame, said method comprising the stepsof:arranging a cooling conduit into a selected configuration; engagingat least one spacer bar to the cooling conduit; and casting the statorframe so that the cooling conduit is at least partially embedded withinthe frame.
 21. A method in accordance with claim 20 wherein the selectedconfiguration for the cooling conduit is a generally helical geometricconfiguration.
 22. A method in accordance with claim 20 wherein theselected configuration for the cooling conduit is a generally serpentinegeometric configuration.
 23. A method in accordance with claim 20wherein the selected configuration is a squirrel cage configuration. 24.A method in accordance with claim 20 wherein casting the stator frame sothat the cooling conduit is at least partially embedded within the framecomprises the steps of:positioning the conduit within metal castingtooling; and injecting molten metal into the tooling and around theconduit.
 25. A method in accordance with claim 24 wherein prior topositioning the conduit within the metal casting tooling, said methodcomprises the step of at least partially embedding the conduit in arigid foam structure.
 26. A method in accordance with claim 20 whereinthe cooling conduit is a first material and the casting material is asecond material.
 27. A stator frame for an electric motor, said statorframe comprising:a substantially cylindrical shaped body sectioncomprising opposed ends, a cooling passageway extending through at leasta portion of said body section, and a wall having an outer surface andan inner surface, said cooling passageway comprises a cooling conduitpartially within said wall between said inner surface and said outersurface; and an inlet port and an outlet port in flow communication withsaid cooling passageway.
 28. A stator frame in accordance with claim 27wherein said cooling conduit comprises an inlet end positioned at saidinlet port and an outlet end positioned at said outlet port.
 29. Astator frame in accordance with claim 27 wherein said cooling conduitfurther comprises an intermediate portion arranged in a generallyhelical geometric configuration.
 30. A stator frame in accordance withclaim 27 wherein said cooling conduit is a first material and said bodyportion is a second material.
 31. A stator frame in accordance withclaim 27 further comprising at least one spacer bar engaged to saidcooling conduit.